The present invention relates to a thin film formation method and, more particularly, to a method of forming a high-quality titanium nitride film which can be suitably used as a conductor film in a semiconductor device or the like.
Conventionally, a thermal CVD method is generally performed in order to form a titanium nitride film on a substrate. In this method, titanium tetrachloride (TiCl.sub.4) and nitrogen (N.sub.2), ammonia (NH.sub.3), or the like are used as source material and heated up to a high temperature of 800.degree. C. or more to be chemically vapor-deposited. In recent years, extensive studies aiming at applying a titanium nitride film to a semiconductor device have been made, and a method of forming a film at a substrate temperature of about 600.degree. C. is proposed in, e.g., U.S. Pat. No. 4,570,328. In this film formation method using a source gas (TiCl.sub.4), however, chlorine atoms having corrosiveness cannot be prevented from being mixed in a formed titanium nitride film. Therefore, it is difficult to apply the method to a semiconductor manufacturing process.
A method of forming a titanium nitride film at a comparatively low temperature is proposed in, e.g., Japanese Patent Publication No. 57-42970. The proposed method is a plasma CVD method in which an RF magnetic field is applied in a vapor phase reaction chamber to decompose and vapor-deposit an organo-titanium compound in a plasma. If this material is used, however, high-temperature reaction conditions are required in this CVD method using only a thermal reaction. In addition, in the plasma CVD method, an organo-titanium compound as a source material is decomposed into carbon (C) or the like as its component, and this decomposed carbon is mixed as an impurity in a formed titanium nitride film. Therefore, it is difficult to form a titanium nitride film with high purity and quality.
As described above, in the conventional thermal CVD method or plasma CVD method, reaction conditions require a high temperature, or a source material is decomposed into carbon or the like as its component and this decomposed carbon is mixed as an impurity in a formed titanium nitride film. Therefore, a high-quality titanium nitride film cannot be formed.